func create(client *pubsub.Client, topic string) error {
	ctx := context.Background()
	// [START create_topic]
	t, err := client.CreateTopic(ctx, topic)
	if err != nil {
		return err
	}
	fmt.Printf("Topic created: %v\n", t)
	// [END create_topic]
	return nil
}
func createTopicIfNotExists(c *pubsub.Client) *pubsub.Topic {
	ctx := context.Background()

	const topic = "example-topic"
	// Create a topic to subscribe to.
	t := c.Topic(topic)
	ok, err := t.Exists(ctx)
	if err != nil {
		log.Fatal(err)
	}
	if ok {
		return t
	}

	t, err = c.CreateTopic(ctx, topic)
	if err != nil {
		log.Fatalf("Failed to create the topic: %v", err)
	}
	return t
}